Deposition of aggregates of misfolded protein into intracellular inclusion bodies is a prominent cytopathological feature of nearly every known neurodegenerative disease. Despite mounting genetic and biochemical evidence linking protein aggregation to pathogenesis in these and other diseases, it is unclear bow -or indeed whether- protein aggregation and inclusion body formation are primary toxic events or cytoprotective responses. My lab has recently described a general pathway by which aggregated proteins in mammalian cells are collected into specialized inclusion bodies called aggresomes (AG). The studies described in this proposal are intended to test the hypothesis that delivery of protein aggregates to AG is a specific, microtubule-dependent transport process which facilitates the neutralization and elimination of potentially toxic gene products. Towards this end, three specific aims are proposed. The first aim will use biochemical and biophysical techniques to study the cellular mechanism of AG formation to identify transport intermediates in AG formation. These intermediates will be subject to extensive biochemical, biophysical and structural characterization. The second aim of the proposed research will be to reconstitute AG formation in a cell-free system in order to identify the cytoplasmic components required for retrograde transport of protein aggregates on microtubule tracks. Finally, the last aim will investigate the role of retrograde transport in the neutralization and elimination of protein aggregates. These last studies will specifically test the hypothesis that retrograde transport of aggregated protein is linked to the lysosomal/autophagic pathway of protein degradation.